The present invention relates generally to devices for removing embolic material from blood vessels, and, more particularly, to an occlusion device (e.g., a balloon) for aspirating a blood vessel, such as the aorta during cardiac surgery, to remove embolic material from the vessel, and to methods of using such a device.
During cardiac surgery, it is often necessary to introduce a cannula into an artery or other blood vessel. For example, an arterial cannula is typically introduced into the aorta to deliver blood from a bypass-oxygenator machine during cardiopulmonary bypass (CPB), as is used during coronary arterial bypass surgery and other procedures. Such a cannula generally includes a proximal end for receiving blood from the bypass-oxygenator machine, a distal end for entry into the artery, and a lumen extending between the proximal and distal ends.
One concern with such procedures is that calcified plaque or other embolic material may be dislodged during the procedure, particularly when clamping or unclamping the aorta. See Barbut et al., xe2x80x9cCerebral Emboli Detected During Bypass Surgery Are Associated With Clamp Removal,xe2x80x9d Stroke, 25(12):2398-2402 (1994), incorporated herein by reference in its entirety, which quantifies the level of embolic release during each step of CPB and explains when protection from embolization is needed. Such embolic material may travel downstream, possibly becoming lodged in another portion of the blood vessel or possibly reaching a vital organ, such as the brain, where the material can cause substantial injury to the patient.
In response to this concern, a blood filter device may be introduced into the blood vessel to capture any embolic material that becomes dislodged within the vessel. For example, a blood filter may be disposed on the distal end of an arterial cannula for capturing embolic material in the vessel into which the cannula is introduced. Filters, however, may have certain disadvantages because as blood flows through the filter, the blood may clot and attach to the filter mesh, possibly impairing flow through the filter, and consequently through the vessel. In addition, the filter may become clogged with embolic material during use, preventing the device from effectively capturing additional material and/or impairing flow through the vessel.
Accordingly, there appears to be a need for a device for removing embolic material from a blood vessel, such as the aorta, that avoids these problems.
The present invention is directed to a device for aspirating embolic material from a blood vessel, such as from the aorta during cardiac surgery, and also from the common carotid artery, external and internal carotid arteries, brachiocephalic trunk, middle cerebral artery, anterior cerebral artery, posterior cerebral artery, vertebral artery, basilar artery, subclavian artery, brachial artery, axillary artery, iliac artery, renal artery, femoral artery, popliteal artery, celiac artery, superior mesenteric artery, inferior mesenteric artery, anterior tibial artery, posterior tibial artery and all other arteries carrying oxygenated blood. In a first preferred embodiment, the device is an arterial cannula with an occlusion device (e.g., a balloon occluder) capable of aspirating a blood vessel and thereby removing embolic material from the vessel. The cannula is a substantially rigid elongate member having a proximal end adapted to receive blood from a bypass-oxygenator machine, a distal end adapted to enter an artery, and a blood flow lumen extending between the proximal end and an outlet on the distal end.
The cannula has an aspiration port proximate to the outlet, which communicates with an aspiration lumen that extends proximally from the aspiration port along the cannula. The cannula also includes an inflatable balloon attached to the cannula between the outlet and the aspiration port, the balloon being capable of assuming an inflated condition for occluding a blood vessel.
To use the device, the distal end of the cannula is introduced into a blood vessel, such as into the ascending aorta upstream of the carotid arteries. The outlet is oriented downstream for delivering blood into the vessel from a bypass-oxygenator machine. The balloon on the cannula is then inflated to occlude the vessel, that is, the balloon expands and engages the wall of the vessel, thereby providing a fluid-tight seal between an upstream portion and a downstream portion of the vessel. Fluid may then be introduced through the aspiration port into the upstream portion of the vessel, sweeping up loose embolic material within the upstream portion. The fluid may then be withdrawn from the upstream portion of the vessel through the aspiration port, for example by connecting the aspiration lumen to hospital suction, thereby aspirating loose embolic material from the upstream portion of the vessel.
In a second preferred embodiment, the device includes an arterial cannula, a first balloon occluder attached to the cannula, and an aspiration port, similar to the embodiment described above. In addition, the device also includes a second balloon occlusion device deployable from the distal end of the cannula, the second balloon also being capable of assuming an inflated condition for further occluding a blood vessel. Preferably, the second balloon is attached to the distal end of an elongate tubular member. The elongate tubular member is slidably received in the aspiration lumen, allowing the second balloon to slidably deployed from and retracted into the aspiration port. Alternatively, a separate lumen may be provided in the cannula for the second balloon occlusion device.
Similar to the previous embodiment, the distal end of the cannula is introduced into a blood vessel, and the outlet is oriented downstream. The first balloon is inflated to occlude the vessel, and substantially isolate an upstream portion of the vessel from a downstream portion.
The second balloon may then be deployed into the upstream portion of the vessel, for example into the aorta towards the coronary arteries. The second balloon may then be inflated to further occlude the blood vessel, and substantially isolate the upstream portion, for example from the coronary arteries, to prevent fluid and/or embolic material from traveling upstream when the upstream portion is flushed.
Fluid may then be flushed into the vessel and aspirated out through the aspiration port as desired to remove loose embolic material from the upstream portion of the vessel. The second balloon may then be deflated, and withdrawn back into the cannula. Upon completion of the procedure, the first balloon may be deflated, and the cannula removed from the vessel.
Thus, a device in accordance with the present invention allows a blood vessel to be dammed downstream from a location in which emboli are likely to be dislodged during the course of a surgical procedure. The region of the vessel upstream of the dam may then be flushed and aspirated as desired, thereby removing embolic material released during the procedure and preventing the embolic material from escaping downstream and potentially injuring the patient.
An additional feature of a balloon occlusion device in accordance with the present invention is that the balloon may serve an additional function besides damming the vessel to allow loose embolic material to be aspirated away. The balloon may substantially engage the walls of the vessel and provide a fluid-tight seal, thereby eliminating the need for other devices to block the vessel, such as a cross clamp which is often used to clamp the aorta during cardiac surgery.
Accordingly, it is an object of the present invention to provide a balloon occlusion device for aspirating embolic material from a blood vessel, which avoids many of the problems of previously known devices, such as blood filters.
Other objects and features of the present invention will become apparent from consideration of the following description taken in conjunction with the accompanying drawings.